AMQ::Client::Exchange#publish no longer takes a callback
AMQ::Client::Exchange#publish no longer takes a callback

 * Semantics of it is constantly misinterpreted by people as "when my data is published". With buffering going on
   inside EventMachine C++ core and underlying glibc and even OS kernel, it is impossible for a Ruby library to know
   "when the data is published".

 * Ideally it should be run on the next event loop tick but to unify that across different networking layers we need
   an extra indirection layer. A lower-level client can be just fine without all these bells and whistles.

travis-repos/amq-client,ruby-amqp/amq-client,ruby-amqp/amq-client,travis-repos/amq-client